(a) Technical Field
The present disclosure relates to a polypropylene-polylactic acid composite composition. More particularly, it relates to a polypropylene-polylactic acid composite composition with excellent heat resistance and mechanical strength thus being useful in the manufacture of vehicle parts materials as well as construction materials.
(b) Background Art
The rapid global industrialization since the late 20th century appears to be largely due to fossil fuel resources, in particular, petroleum resource. The effort toward full-fledged industrialization has been boosting up the use of petroleum along with the global increase in population. However, petroleum is not a recyclable resource and also its global reservoir appears to be very limited. Further, as petroleum produces carbon dioxide, which has been claimed as a main cause of global warming, there have been many lines of research working on how to reduce carbon dioxide emission and avoid use of petroleum.
Plant-derived biomass polymers can be obtained from recyclable plant resources such as corns, beans, sugar cane, woods or the like by means of chemical or biological means. They appear to be more effective than biodegradable materials in coping with environmental issues including carbon dioxide reduction. Of the biomass polymers, polylactic acid is a linear aliphatic polyester which can be prepared by fermentation of starch of corn or potato, or by polymerization of sugar monomers obtained by fermentation of saccharified plant cellulose. It is a carbon neutral eco-friendly thermoplastic polymer.
However, polylactic acid resin has poor physical properties as compared to those of conventional polymer materials and thus its industrial application is much limited. More particularly, in order for polylactic acid to be used as automotive materials, it is essential to remedy its heat resistance and impact resistance. For this reason, there have been many attempts to develop composite materials by blending it with polypropylene resin, a conventional petroleum-based resin.
Polypropylene resin, however, is not compatible with polylactic acid resin due to difference in polarity between the two, methods of adding a compatibilizer have been attempted. For example, Japanese Patent Application Publication Nos. 2009-096892 and 2009-256487 disclose methods of adding noncrystalline polypropylene grafted by anhyrdrous maleic acid as a compatibilizer to improve the compatibility between polylactic acid resin and polypropylene resin. The compositions taught by the references were shown to have excellent impact strength but their tensile property was poor.
Japanese Patent Application Publication No. 2008-111043 teaches a method using ethylene-propylene copolymer grafted by anhyrdrous maleic acid as a compatibilizer. The composite material taught by the reference reveals that it has a good heat resistance but its impact strength is not good enough to be used for the manufacture of automotive materials. The reference also discloses a method of using amino-modified elastomer as a compatibilizer to obtain a composition having excellent properties in both heat resistance and impact strength. However, the resultant did not have sufficient property to be used as a material for interior and exterior parts of a vehicle.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.